In recent years, light emitting diodes (hereinafter referred to as “LED”) have been used as a light source for lighting from the perspective of energy saving and miniaturization. Moreover, light source units for radiating light (light emitting device) each including an LED and an optical element for converting light direction (light flux controlling member) configured to control the distribution of light emitted from the LED combined with each other have been increasingly used instead of fluorescent lighting or halogen lamps (see for example PTL 1).
FIG. 1 is a cross-sectional view of a light source unit for radiating light 10 disclosed in PTL 1. Substrate 40 on which light source unit for radiating light 10 is mounted is shown by a broken line in FIG. 1. As illustrated in FIG. 1, light source unit for radiating light 10 disclosed in PTL 1 comprises LED 20 and optical element for converting light direction 30 disposed at a position intersecting optical axis LA of the light flux emitted from LED 20. Optical element for converting light direction 30 comprises incidence surface 31 on the LED side (rear side), reflection surface 32 disposed on the opposite side to incidence surface 31 (front side), emission surface 33 on the lateral side, and inclining surface 34 connecting incidence surface 31 with emission surface 33. In a plane including optical axis LA of light emitted from LED 20, inclining surface 34 is disposed so that the distance from LED 20 increases as the distance from optical axis LA increases.
The light emitted from LED 20 is incident on incidence surface 31, reflected laterally by reflection surface 32, and then emitted from emission surface 33 laterally. It is to be noted that the light emitted from LED 20 does not enter optical element for converting light direction 30 from inclining surface 34. The light emitted from LED 20 is thus controlled to be emitted laterally by optical element for converting light direction 30 in light source unit for radiating light 10 disclosed in PTL 1.